Originally Posted by
Kontact
Reading the OP, I can't tell if he's having blow offs. If the tube suddenly failed internally due just to melting, I don't see why you wouldn't get a popping noise as the pressure escaped out through the rim. Many would call that a "blow out".
The OP ought to relate whether the bead came off or not, and what the tube looked like.
People can hypothesize day and night about melting (actually softening) tubes, how they might fail, and what they may sound like when they fail, but here's something that is unequivocal:
The common heat-induced failure mechanism is tire blow-off, caused by overpressure [EDIT: and the softening of the tire's bead]. It has been happening the same way, ever since cyclists with clincher tires started descending steep roads. Without exceeding the temperature limit of a butyl tube, an overpressure of 50% is possible, which is more than enough to blow a tire. Braking steadily for 30 seconds on a steep downhill will do the trick.